It has heretofore been proposed that closures be provided for containers wherein the closures include a cap that is hinged to the part of the closure on the container by an integral hinge. Conventionally, such closures rely on tension and elastic elongation of the hinged components to produce a snap action. Typical constructions are shown in U.S. Pat. Nos. 3,628,215, 3,629,901, 3,933,271, 4,047,495, 4,386,714. U.S. Pat. No. 4,545,495 shows a closure wherein a collar is connected to a cap by a main hinge and connecting elements which are straight when the closure is in closed position and have a non-linear configuration lying in a plane parallel to the main hinge axis when the closure is in open position. The skirt of the cap is elastically deformable adjacent the main hinge so that the skirt bends inwardly when the cap moves from an open position to a closed position.
Among the objectives of the present invention are to provide a dispensing closure which has a cap that operates with a snap action in moving to and from a closed position; which closure does not rely on tension of the hinge; which has minimum hinge protrusion so that it is compatible with high speed filling lines thus allowing greater line speeds; which provides a low profile; and which is relatively easy to manufacture.
In accordance with the invention, the closure with a snap type hinge cap comprises a first part adapted to interengage with the open neck of a container and a second part forming a cap. Each of the first and second parts comprises a base wall and a peripheral skirt. A pair of hinges extends between the skirt of the first part and the skirt of the second part to hinge the parts about a hinge line. A short strap connects the skirt of the first part and the skirt of the second part circumferentially between the hinges. The short strap is axially rigid and has its ends hinged to the skirt of the first part and the skirt of the second part, respectively. The radial length of the strap is less than the length of the arc through which the second cap part is guided by movement by the hinges to and from open and closed positions relative to the first part. The portion of the skirt of the second part to which the strap is connected is capable of flexing. The strap causes the flexing skirt of the second part to deflect while rotating between open and closed positions by pulling the skirt against its normal path. The reaction of the skirt to this pulling action is to tend to force the second part to remain open, or to tend to close the second part after sufficient rotation is made in the closing motion.